1. Field of the Invention
The present invention relates to a combustion apparatus used in a device such as a water heater.
2. Description of the Related Art
Recently, water heaters are in widespread use at home. Water heaters for household use must supply hot water to a number of places solely by itself. For example, each family has water taps or showers in a kitchen, a bathroom, a washbasin in its house. One water heater supplies hot water to those. Further, a large number of water heaters for household use have functions such as filling a bathtub with hot water and heating a remaining bath water again.
In this way, since hot water is used at a plurality of places by using a water heater for household use, the required amount and temperature of water change frequently. Thus, a combustion apparatus incorporated in such a water heater must change a combustion amount in response to a change of the amount and temperature of water.
For that reason, a combustion apparatus incorporated in a water heater for household use is provided with a gas proportional valve so as to change the combustion amount. More specifically, the combustion amount is changed by controlling the amount of fuel gas by regulating a valve opening degree of the proportional valve, which is disposed at a fuel supply channel of the combustion apparatus, in response to the required amount of heat generation.
The patent document 1 specified below discloses a combustion apparatus provided with a proportional valve at a fuel gas supply channel.    Patent Document 1: JP 2000-146163 A